Monitoring and determination of the true volume status of patients subjected to trauma / hemorrhage by means of conventional vital signs (heart rate, blood pressure, arterial oxygen saturation) is complex because their changes are late in the progression of trauma. The compensatory response to hemorrhage is guided by the autonomic nervous system sympathetic and parasympathetic. The literature has demonstrated that heart rate variability (HRV) can be used to monitor the compensatory autonomic response of patients and can detect the deterioration of their physiological reserve, identifying patients with inadequate compensatory response. The primary objective of this study is to evaluate the behavior of indirect measures of HRV (LF / HF and HF) in pigs during hemorrhagic shock and after fluid resuscitation with crystalloid solution. Will be used 16 young pigs subjected to hemorrhage of 60% volume and evaluated for a period of 60 minutes without fluid replacement. After this period, the animals the animals will be divided into survivors and nonsurvivors. The surviving animals are treated with Ringer solution and evaluated for a period of 180 minutes. The hypothesis to be investigated in this study is that autonomic dysfunction is related to the fact that some patients do not develop an adequate compensatory response to severe bleeding and there is a positive correlation between measures of heart rate variability, the progression of hemorrhagic shock and fluid resuscitation, so that such information may be clinically useful as early predictors of survival in the presence of severe bleeding.
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